Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Pixel Art Studio - A purpose-built drawing tool for pixel artists
Sketch - Professional digital design for Mac.
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Affinity Designer - Professional creative software, exclusively for Mac.
Pixel Studio - The Pixel Art Is Always Fun